1. Field of the Invention
The present invention relates to an integrated semiconductor circuit, in particular a semiconductor memory configuration, which can be operated in various operating modes and which, for this purpose, has an apparatus for switching between the operating modes, and to a method for operation of an integrated semiconductor memory configuration.
In general, integrated semiconductor circuits, in particular integrated semiconductor memory configurations, are provided with one or more additional pads in order to make it possible to change reliably between the different operating modes or test modes at the wafer level. If such an additional pad is then externally raised to a predetermined voltage value, then the integrated semiconductor circuit changes to a different operating mode. X pads make it possible to change between 2x modes.
For example, in the case of the integrated semiconductor memory configuration, the term xe2x80x9cvarious operating modesxe2x80x9d refers to a xe2x80x9cnormalxe2x80x9d operating mode, as is also used by the user, and to other operating modes other than the normal mode. In which, for example, the functionality of the interface is changed, together with modes which change the conditions in which the memory chip is operated, and which are generally referred to as test modes. Such different modes are, for example, xe2x80x9cRAMBUSxe2x80x9d, the normal operating mode, the DA MODE, and the drowsy mode.
A chip at the wafer level has various pads and associated contactors. Where no contact is made with the corresponding pads, the chip is in a customer mode which, by way of example, is referred to here as a first mode or mode one.
The chip can be changed to a second mode (i.e. mode two) by actuation of the mode pad. After being packaged, when the chip is then in the form of a module, only the first mode (one) is possible.
The need for such an additional mode pad can arise when it is intended to operate a memory chip at the wafer level with a different interface functionality, with contactors which differ for different functionalities of the interface, generally needle boards, being used for the modes. If one of the needle boards now does not make contact with all the pads which are necessary to change the chip to the other mode by externally applying a combination of signals to the pads, then this can nevertheless be achieved by raising the additional pad to the appropriate voltage.
Such an additional pad is not connected to the package contacts in the chip. This avoids a user inadvertently changing to a different operating mode.
It is accordingly an object of the invention to provide an integrated semiconductor circuit, in particular a semiconductor memory configuration, and a method for its operation which overcome the above-mentioned disadvantages of the prior art devices and methods of this general type, in which an additional pad or the additional pads in an integrated semiconductor circuit are avoided, and to allow reliable switching between various operating or test modes in such integrated semiconductor circuits.
With the foregoing and other objects in view there is provided, in accordance with the invention, an integrated semiconductor circuit. The circuit contains a switching apparatus for switching between various operating modes. The switching apparatus has at least one fuse unit able to be blown when the integrated semiconductor circuit is in a packaged state. The fuse unit can be programmed by fuse soft set programming and can be blown at a wafer level, and a blown state of the fuse unit being bridged by the fuse soft set programming of the fuse unit.
According to one major aspect of the invention, the integrated semiconductor circuit, in particular a semiconductor memory configuration, which achieves the above object and can be operated in various operating modes has an apparatus for switching between the operating modes. The switching apparatus has at least one fuse unit that can be blown when the semiconductor circuit is in the packaged state, and is characterized in that the fuse unit is a fuse unit which can be programmed by a xe2x80x9cfuse soft setxe2x80x9d, can also be blown at the wafer level of the integrated semiconductor circuit, and in which the blown state can be bridged by a programmed fuse soft set.
The use of the programmable operating mode fuse results in that there is no longer any need to provide an additional pad for changing between the various operating modes. The operating mode fuse is blown, that is to say it is disconnected, in order to change the chip to the normal operating mode before encapsulation in a package.
Since the operating mode fuse can also be programmed (xe2x80x9cfuse soft setxe2x80x9d), it is also possible to change between the modes in the packaged module.
Normally, the information in the fuse (blown or disconnected or not) is read only once after the external supply voltage has been raised, so that the memory chip remains in the respectively set operating mode for as long the external voltage is applied. In order, for example, that the chip can be measured using a needle board even immediately after production but before blowing of a fuse unit, with the needle board being based on the functionality of the interface for the operating mode other than the normal mode, the operating mode selection circuit, which is connected to the switching apparatus and decides the operating mode that the chip will be in once the supply voltage has been raised, can automatically select the operating mode other than the normal mode. The selection of the operating mode after the supply voltage has been raised, can be, but need not necessarily, be linked to the programmable fuse unit.
In accordance with an added feature of the invention, the switching apparatus is configured such that, in response to the fuse soft set programming of the fuse unit without the fuse unit being blown, the switching apparatus sets an operating mode corresponding to the blown state of the fuse unit.
In accordance with another mode of the invention, the switching apparatus is configured such that, in response to the fuse unit being blown before the integrated semiconductor circuit is packaged in a package, the integrated semiconductor circuit changes to the normal operating mode.
In accordance with an additional mode of the invention, the switching apparatus is configured such that, in the packaged state, the integrated semiconductor circuit can change between the various operating modes, even when the fuse unit is in the blown state, by the fuse soft set programming of the fuse unit.
In accordance with a further feature of the invention, the switching apparatus is configured such that, at the wafer level and immediately after production when a supply voltage is raised, the switching apparatus automatically sets the integrated semiconductor circuit to an operating mode other than the normal operating mode.
In accordance with a further added feature of the invention, the switching apparatus selects the operating mode other than the normal operating mode by the fuse soft set programming of the fuse unit.
In accordance with a further additional feature of the invention, the switching apparatus selects the operating mode other than the normal operating mode without the fuse soft set programming of the fuse unit.
In accordance with another further feature of the invention, the fuse unit is configured for storing and for reading its information.
In accordance with a concomitant feature of the invention, the integrated semiconductor circuit is a semiconductor memory configuration.
With the foregoing and other objects in view there is also provided, in accordance with the invention, a method for operation of an integrated semiconductor memory configuration. The method includes using a switching apparatus having at least one fuse unit able to be blown and able to be programmed by fuse soft set programming. The switching apparatus is used for selecting between different operating modes. The fuse unit is blown at a wafer level and, in response to the fuse unit being blown, the integrated semiconductor memory operates in a normal operating mode.
In accordance with an added mode of the invention, there is the step of automatically switching to an operating mode other than the normal operating mode immediately after production and when a supply voltage is raised.
In accordance with an additional mode of the invention, there is the step of storing and reading back information in the fuse unit immediately after a power-up condition is detected.
In accordance with a further mode of the invention, there is the step of carrying out a front end test when the fuse unit is in an unblown state.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in an integrated semiconductor circuit, in particular a semiconductor memory configuration, and a method for its operation, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.